Image forming apparatus with obtuse-edge cleaning blade

Abstract

An image forming apparatus of the present invention includes a cleaning brush positioned upstream of a blade nip in the direction of movement of the surface of a photoconductive drum. To prevent toner from accumulating at the blade nip, the surface of the photoconductive drum is moved in the direction opposite to the regular direction for image formation, conveying toner accumulated in a wedge-shaped space upstream of the blade nip 2 n to a position where the cleaning brush removes it. With this configuration, the image forming apparatus can stably clear spherical toner particles left on the drum over a long period of time.

1. An image forming apparatus comprising:
 a toner image carrier whose surface is movable while carrying a toner image thereon; 
 cleaning means including a cleaning blade held in contact with the surface of said toner image carrier in a counter direction for removing toner particles left on said surface; and 
 toner accumulation preventing means for preventing the toner from accumulating at a blade contact portion where said toner image carrier and said cleaning blade contact each other; 
 wherein the toner, forming the toner image, comprises spherical toner having circularity of 0.98 or above, and 
 two surfaces of said cleaning blade, forming a ridge line contacting said image carrier, form an obtuse edge angle with each other before the cleaning blade is positioned for use by contacting said toner image carrier. 
 
   
   
     2. The apparatus as claimed in  claim 1 , wherein said toner image carrier comprises a latent image carrier. 
   
   
     3. The apparatus as claimed in  claim 1 , wherein said toner image carrier comprises an intermediate image transfer body. 
   
   
     4. The apparatus as claimed in  claim 1 , wherein said obtuse edge angle is between 95° and 120°. 
   
   
     5. The apparatus as claimed in  claim 1 , wherein said cleaning blade has rubber hardness of between 65° and 80° in JIS (Japanese Industrial Standards)-A scale. 
   
   
     6. The apparatus as claimed in  claim 1 , wherein said cleaning blade has a modulus of repulsive elasticity of 30% or below at normal temperature of 24° C.±3° C. and varies by a ratio of 350% or below in a range of from 10° C. to 40° C. 
   
   
     7. The apparatus as claimed in  claim 1 , wherein said cleaning blade exerts a linear pressure of 0.50 N/cm or above on said toner image carrier when said toner image carrier is held in a halt. 
   
   
     8. The apparatus as claimed in  claim 1 , wherein at least said cleaning means and said toner image carrier are constructed into a single process cartridge removably mounted to an apparatus body. 
   
   
     9. The apparatus as claimed in  claim 1 , wherein a surface layer, forming the surface of said toner image carrier, comprises a protection layer implemented by a binder resin having a bridged structure, and
 the binder resin contains a charge transporting substance in the structure thereof. 
 
   
   
     10. The apparatus as claimed in  claim 1 , further comprising:
 toner removing means for removing the toner from the surface of said image carrier at a side upstream of said blade contact portion in a regular direction of movement of the surface of said image carrier; 
 removal control means for moving the surface of said toner image carrier in an opposite direction opposite to the regular direction for thereby causing said surface to convey accumulated toner accumulated at the side upstream of said blade contact portion to a position where said toner removing means is positioned, whereby said accumulated toner is removed by said toner removing means; 
 wherein said toner removing means and said removal control means constitute said toner accumulation preventing means. 
 
   
   
     11. The apparatus as claimed in  claim 10 , wherein a toner removing mode for removing the accumulated toner starts after an image forming operation has ended. 
   
   
     12. The apparatus as claimed in  claim 10 , wherein said removal control means causes said toner removing means to remove the toner from the surface of said toner image carrier such that said toner remains on said surface of said toner image carrier in an amount of between 0.01 mg/cm 2  and 0.1 mg/cm 2 . 
   
   
     13. The apparatus as claimed in  claim 10 , wherein a toner removing mode for removing the accumulated toner starts when the surface of said toner image carrier is rotated a preselected number of times. 
   
   
     14. The apparatus as claimed in  claim 10 , wherein said toner removing means comprises a brush member configured to remove the toner from the surface of said toner image carrier while rotating in contact with said surface. 
   
   
     15. The apparatus as claimed in  claim 14 , further comprising bias applying mans for applying a voltage to said brush member;
 wherein when the surface of said toner image carrier is moved in the opposite direction, said brush member is caused to rotate and applied with a bias of a same polarity as a regular electrification characteristic of the toner, which is assigned to usual image formation, from said bias applying means. 
 
   
   
     16. The apparatus as claimed in  claim 14 , further comprising bias applying means for applying a voltage to said brush member;
 wherein when the surface of said toner image carrier is moved in the opposite direction, said brush member is caused to rotate and applied with a bias of an opposite polarity as a regular electrification characteristic of the toner, which is assigned to usual image formation, from said bias applying means. 
 
   
   
     17. The apparatus as claimed in  claim 14 , wherein bristles of said brush have a length between 0.5 mm and 10 mm.